CHARLOTTE, N.C. (AP) — Barack Obama goes before his convention with a reputation as a great orator.

But is he?

Certainly, there have been moments that soared: his address to the 2004 convention and that moving election night in Chicago. Yet a close look at pivotal moments of his presidency finds that, more often than not, Obama has fallen short as a communicator.

That's the conclusion of one of the leading experts on presidential communications, Kathleen Hall Jamieson. Repeatedly, she asserts, Obama has failed to use the communication power of his office to further his goals and rally the country. So now he goes into his crucial convention speech with high expectations from his successes and yet a mixed record as communicator-in-chief.

Jamieson, a professor of communications at the University of Pennsylvania, examined six pivotal moments for an article in the next issue of Polity, a political science journal. She found that in five, Obama did not deliver.

Sometimes the problem was the writing. Sometimes it was the stage management. In one case he just had nothing to say.

Here are her six cases:

___

ELECTION NIGHT 2008

The moment a candidate is elected president, his role shifts. Obama handled this transition well in his speech from Grant Park in Chicago. He praised his opponent, John McCain, and reworked his campaign slogan — "Yes, we can" — into "a shared commitment to a common vision," Jamieson says.

"To those Americans whose support I have yet to earn," Obama said that night, "I may not have won your vote tonight, but I hear your voices. I need your help. And I will be your president, too."

The country was moved, and Obama's reputation for oratorical skill was reinforced.

___

LINCOLN MEMORIAL

But things began to go badly, rhetorically speaking, even before Obama took office.

As the candidate becomes president-elect, "any subsequent lapse into campaign rhetoric is role-shattering," Jamieson says. But that is precisely what happened two nights before his inauguration. Obama went to the Lincoln Memorial and delivered "a maladroit response to the role of president-elect," addressing his supporters rather than the whole country.

"Yours are the voices I will take with me every day I walk into that Oval Office," Obama told supporters.

Jamieson said "Obama violated a requirement of pre-inaugural rhetoric when he shifted from his rhetoric of shared interest to ... a reprise of his stump speech."

___

FIRST INAUGURAL

Inaugural addresses are among the nation's ultimate communal moments. To be effective, Jamieson says, inaugural addresses need a moment that digests the core ideas into a single memorable phrase. This need precedes even the age of sound bites, as illustrated by Thomas Jefferson ("We are all Republicans, we are all Federalists") and Franklin D. Roosevelt ("The only thing we have to fear is fear itself").

Obama failed to do this, Jamieson asserts. Press coverage searched in vain for "the intended core of the address," grabbing disparate phrases from the speech, such as "new era of responsibility" and "starting today, we must pick ourselves up, dust ourselves off, and begin again the work of remaking America."

"Unsurprisingly, then," Jamieson concluded, "the fact that the country's first African-American president delivered the 2009 inaugural is more fixed in memory than any statement from it."

___

OIL SPILL

Obama's first Oval Office speech was in response to the Gulf oil spill. Obama had made environmental "peril" a campaign theme, saying it was urgent to act so that "this was the moment when the rise of the oceans began to slow and our planet began to heal."

This created expectations for action when Obama spoke to the country about the oil spill, Jamieson says. With oil surging into the Gulf from a blown BP well, Obama noted that as a candidate he had "laid out a set of principles that would move our country toward energy independence." The House of Representatives had passed legislation to enact these principles. But instead of pressing for the Senate to follow, Jamieson says, "President Obama temporized and conciliated," apparently knowing he didn't have 60 votes in the Senate.

"I'm happy to look at other ideas," the president told the nation.

The speech also made no attempt to invoke the "heartbreaking images of oil drenched sea birds and tarred beaches," Jamieson says. "As a result of these failures, a speech with the potential to be presidency-defining instead proved unmemorable."

___

TUCSON MEMORIAL

Presidents can use moments of national trauma to help the nation build meaning and heal together. Ronald Reagan did that after the Challenger exploded in 1986; Bill Clinton did after the Oklahoma City bombing in 1995.

President Obama faced such a moment when a gunman shot Representative Gabrielle Giffords and 18 others at a town meeting in Tucson. Obama's speech was well-crafted. Political opponents complimented the president. But the setting and Obama's delivery undercut his moment, Jamieson says. The eulogy was delivered in a sports arena in front of 14,000 people who responded with applause rather than amens or contemplation.

Responding to the applause, "the pace of the president's delivery quickened and his intensity increased as he spoke the address's most memorable lines." He made the speech fit the hall, not the moment, Jamieson says, and he offered a "delivery more similar to a stump speech than a eulogy."

She concludes that "an eloquently written speech was undercut by maladroit stage management."

___

DOWNGRADE OF AMERICA

On August 8, 2011, the stock market was cratering. The previous Friday evening Standard & Poor's, the bond rating agency, had downgraded America's credit. The government had failed to show it would curb deficit spending, the rating agency said. By noon the Dow had plunged by 2.75 percent.

The White House said the president would speak at 1 p.m. Cable channels began showing split screens of the falling market and the state dining room where the president was due to speak. 1 p.m. came and went. So did 1:15 and 1:30.

The president appeared, at last, at 1:52 p.m. "The speech that followed was not worth the wait," Jamieson says. "President Obama's response to the crisis was both poorly crafted and inadequately delivered."

Substantively, Obama had no effective response to the Standard & Poor's claim that the government was gridlocked. It was. The best rejoinder was offered by Warren Buffett, who that morning announced that the S&P action shook his faith in S&P, not the United States. Buffett said he would maintain his $40 billion investment in treasury bills. "Inexplicably," Jamieson says, "Obama omitted that central piece of evidence."

Beyond substance, the presentation was flawed. Obama's eyes moved back and forth between teleprompters, and he pursed his lips.

"Magnifying the speech's sense of detachment was the fact that Barack Obama is not adept at sounding empathetic," Jamieson says. Economic struggle and congressional gridlock were treated in the same tone. Says Jamieson, "To ask what difference this incapacity to communicate empathy makes, one need only imagine the same speech delivered by Bill Clinton or Ronald Reagan."

The market continued to fall. "He would have been better advised not to speak, rather than speak ineffectually," Jamieson says. "His credibility as a leader was damaged by the failed attempt."

___

THIS MAY ALL seem mere academic deconstruction. But there are other such critiques, even from allies of the Obama administration.

Much of what voters think about a president is shaped by these moments. Ronald Reagan, with his blend of oratory and ability to convey empathy, demonstrated that dramatically. Not so this year's incumbent.

"As he enters the general election campaign of 2012," Jamieson concludes, "President Obama is a president without an armament of memorable defining statements that recap his vision and, within it, his successes."

That's a lot to repair. Even with the most eloquent of convention speeches.

___

EDITOR'S NOTE — Michael Oreskes, a veteran political reporter and editor, is senior managing editor for U.S. news at The Associated Press.